PSI - Issue 23

Golta Khatibi et al. / Procedia Structural Integrity 23 (2019) 475–480 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

476

2

1. Introduction

Key machinery components used for diminishing, transporting or processing massive volumes of material in heavy industries such as steel, cement or mining are repetitively exposed to severe combinations of different wear mechanisms, for example abrasion and fatigue (Fig. 1a,b) (Hawk 2000). The microstructure and wear properties of state of the art iron based welding alloys used as surface protection do not only depend on the nominal chemical composition of the welding consumables and their manufacturing route, but also on the base material, variations in process technology as well as applied welding parameters (Badisch 2008). Most commonly used ways to characterize weld overlays such as hardness measurements, microstructural investigations or wear testing methods are either slow, expensive or not providing a complete understanding about material behavior of surface coatings exposed to combined wear including fatigue (Franek 2009). The objective of this investigation was therefore to prove the concept of using ultrasonic fatigue testing as new method to understand and predict the behavior of welded surface coatings in a fast and reproducible way. In the study two flux cored wires from different manufacturing lines, but of the same nominal chemical composition were compared applying identical welding parameters. As a result, the two wires could be distinguished clearly by applying the ultrasonic fatigue test method which correlate very well with the response of the weld overlay during the application.

Fig. 1. Examples of application: (a) worn roll of roller press in cement industry, (b) welded roll.

2. Experimental procedure

2.1. Materials

The base metal was a steel bar AISI 4145H Mod. 42CrMo4 type with a hardness of 32-34 HRC and the welding consumables were flux cored wires (TeroMatec OA 4923) with a diameter of 2.8 mm, same chemical composition and two different manufacturing routes. The nominal hardness of the pure all weld metal at 20°C was 55-59 HRC.

Table 1. Nominal chemical composition of the base metal and welding consumables (wt%). Material C Si Mn P S Cr Mo Ti Ni Cu

V Al

AISI 4145H Mod

0.44

0.24

1.11

0.008

<0.004 1.26

0.34

0.22

0.11

0.04 0.016

OA4923

1.9

6.5

1.5

5.5

2.2. Sample preparation

Since ultrasonic fatigue testing requires a defined sample geometry, a special sample design was developed for preparation of the welded joints. The steel bar was cut to obtain discs with a thickness of 20 mm and diameter of 241 mm. A U-shaped groove with a diameter of 20 mm and a depth of 13 mm was cut along the mid-center of each disc and was subsequently filled by using the two flux cored welding wires with the composition given above in order to obtain two sample series (Fig. 2a, b). Open Arc welding was performed without preheating of the base metal with